Where on Earth Are the Best-50 Time Servers?

© 2019, Springer Nature Switzerland AG. We present a list of the Best-50 public IPv4 time servers by mining a high-resolution dataset of Stratum-1 servers for Availability, Stratum Constancy, Leap Performance, and Clock Error, broken down by continent. We find that a server with ideal leap performance, high availability, and low stratum variation is often clock error-free, but this is no guarantee. We discuss the relevance and lifetime of our findings, the scalability of our approach, and implications for load balancing and server ranking

Past, Present and Future of a Habitable Earth

This perspective of this book views Earth's various layers as a whole system, and tries to understand how to achieve harmony and sustainable development between human society and nature, with the theme of " habitability of the Earth." This book is one effort at providing an overview of some of the recent exciting advances Chinese geoscientists have made. It is the concerted team effort of a group of researchers from diverse backgrounds to generalize their vision for Earth science in the next 10 years. The book is intended for scholars, administrators of the Science and Technology policy department, and science research funding agencies. This is an open access book

Long-term trends in particulate matter from wood burning in the United Kingdom: Dependence on weather and social factors

Particulate matter from wood burning emissions (Cwood) was quantified at five locations in the United Kingdom (UK), comprising three rural and two urban sites between 2009 and 2021. The aethalometer method was used. Mean winter Cwood concentrations ranged from 0.26 μg m-3 (in rural Scotland) to 1.30 μg m-3 (London), which represented on average 4% (in rural environments) and 5% (urban) of PM10 concentrations; and 8% of PM2.5. Concentrations were greatest in the evenings in winter months, with larger evening concentrations in the weekends at the urban sites. Random-forest (RF) machine learning regression models were used to reconstruct Cwood concentrations using both meteorological and temporal explanatory variables at each site. The partial dependency plots indicated that temperature and wind speed were the meteorological variables explaining the greatest variability in Cwood, with larger concentrations during cold and calm conditions. Peaks of Cwood concentrations took place during and after events that are celebrated with bonfires. These were Guy Fawkes events in the urban areas and on New Year's Day at the rural sites; the later probably related to long-range transport. Time series were built using the RF. Having removed weather influences, long-term trends of Cwood were estimated using the Theil Sen method. Trends for 2015-2021 were downward at three of the locations (London, Glasgow and rural Scotland), with rates ranging from -5.5% year-1 to -2.5% year-1. The replacement of old fireplaces with lower emission wood stoves might explain the decrease in Cwood especially at the urban sites The two rural sites in England observed positive trends for the same period but this was not statistically significant

Past, Present and Future of a Habitable Earth

This perspective of this book views Earth's various layers as a whole system, and tries to understand how to achieve harmony and sustainable development between human society and nature, with the theme of " habitability of the Earth." This book is one effort at providing an overview of some of the recent exciting advances Chinese geoscientists have made. It is the concerted team effort of a group of researchers from diverse backgrounds to generalize their vision for Earth science in the next 10 years. The book is intended for scholars, administrators of the Science and Technology policy department, and science research funding agencies. This is an open access book

Quantifying impacts of climate change on headwater streamflow regime in Robinson Forest: Insights from 35-years of data collection.

Climate change may shift patterns of streamflow permanence in headwater systems by altering the frequency, magnitude, duration, timing, and rate of change of surface streamflow, impacting both local ecosystems as well as regional water budgets and availability. While much uncertainty surrounds modeling-based methods to quantify the impacts of climate change on water budgets, long-term hydrologic data collected from headwaters in experimental research forests serve as critical evidence to reduce such uncertainty. The objective of this study is to quantify shifts in frequency, magnitude, duration, timing, and rate of change of streamflow in two headwater catchments with relatively little recent disturbance on the Cumberland Plateau using a suite of emerging hydrological statistics and trend analyses. This study determined that each catchment resulted in different streamflow permanence trends over time. Climate and evapotranspiration (ET) may have a significant impact on processes impacting streamflow permanence in each catchment as the major structural differences between the two catchments are slope and aspect

Out in the Open: A Geoarchaeological Approach to Open-Air Surface Archaeology in the Semi-Arid Interior of South Africa’s Western Cape

Southern African research into the behavioural evolution of Late Pleistocene human adaptability, flexibility, and innovation is typically pursued through the lens of rock shelter deposits. However, rock shelters only cover a very small, geographically specific area of the subcontinent, distorting our understanding of change in human-environment interaction and demography. While still under-represented and under-explored in regional syntheses, more studies are looking to open-air archaeology to fill this geographic void in Late Pleistocene research. These studies either pursue a landscape approach that prioritises spatial coverage, or site-bound excavation to maximise temporal control. However, few investigate the depositional and erosional phenomena involved in the formation of surface archaeology and its surrounding landscape. To rectify this disparity, this thesis explores the complex spatio-temporal relationship between surface archaeology and the formation history of Uitspankraal (UPK) 7 by combining multiple interdisciplinary methods from the Earth and archaeological sciences: randomised surface survey and sampling, geomorphometry, geophysical survey, granulometry, XRD analysis, OSL dating, artefact mapping, and assemblage composition and artefact condition analysis. UPK7 is located in the semi-arid Doring River valley and yields surface archaeology that implies occupation from the Still Bay to the Historic period. Results show that it is an eroding series of source-bordering dunes draped across a palaeoterrace and a hillslope of bedrock and colluvium. UPK7 formed through rapid but pulsed sediment accumulation over at least the last 80 ka, with periods of surface deflation and exposure that facilitated artefact redistribution. Despite the abundance of Late Pleistocene archaeology at UPK7, erosion currently outpaces deposition and deposit stabilisation. Erosion has accelerated in at least the last 5,000 years and especially within the last 300 years, suggesting feedback between Holocene aridification, an increase in oscillations between wet-dry conditions, and an increase in human-ungulate activity in the study area. Together these conditions have differentially erased younger deposits, exposing the consolidated Late Pleistocene sediment and the more ancient material it preserves. The visibility, spatio-temporal distribution, and preservation of UPK7’s surface artefacts reflect the locality’s topography, the timing of their discard and the duration and process of sediment accumulation and erosion. The spatial patterning and diversity of time-diagnostic and non-diagnostic artefacts is shown to correspond with the depositional age of their underlying substrate in areas where topographic conditions minimize or reduce the impact of surface runoff, but where sediment deflation persists. When artefacts are assessed at the scale of the archaeological epoch the spatial distribution of Middle Stone Age artefacts shows a significant association with the oldest deposit, Lower Red. The spatial distribution of Later Stone Age artefacts is significantly associated with Upper Yellow sediment, as opposed to the older Lower Red substrate and the younger Indurated Sand. The findings presented in this thesis caution against forming behavioural interpretations from spatial patterns in surface material without examining their post-depositional history and without forming an understanding of the coevolution of archaeological and landscape formation. This study underscores the need for incorporating a geoarchaeological approach into Late Pleistocene open-air research to improve southern Africa’s landscape-scale insight into greater Africa’s human behavioural evolution

Electricity supply in NSW: Alternatives to privatisation

The Public Interest Advocacy Centre (PIAC) commissioned the Institute for Sustainable Futures (ISF) at the University of Technology, Sydney (UTS) to consider the economic case for and against privatisation of electricity assets in NSW. The report, Electricity supply in NSW: alternatives to privatisation, reviews Australian and international experiences with electricity privatisation, critically examines the case for privatisation made by the Owen Report and proposes alternatives that have the potential to deliver a more sustainable future for the NSW electricity industry

Development of a Semi-autonomous Holonomic Load Carrier with Multi-camera Perception

Master's thesis in Mechatronics (MAS500)This thesis documents the development of a load carrier capable of carrying ten advanced personal robots. The robots of concern are Segway Robotics’ Loomo,which are used for education purposes at the University of Agder. They are used at multiple locations on campus, and it is desired to develop a system that can effectively transport them around. The report covers the concept generation, mechanical design, electrical design and development of a navigation system. A simple and compact design was developed and built. To achieve holonomic drive, the rig was equipped with four mecanum wheels. A mechanical design process was performed tocome up with a solution for mounting the wheels to the rig. This included design of an axle and bearing calculations. Additionally, the stability of the rig had to be verified. Further on,to drive the mecanum wheels, four brushless dc motors were utilized. The system consist of multiple hardware components, which needed to communicate with each other. The solution for this is documented in this report

The role of fully coupled ice sheet basal processes in quaternary glacial cycles

Bed conditions such as meltwater pressurization and unconsolidated sediment cover (soft versus hard bedded) strongly impact ice sheet sliding velocities. How the dynamical processes governing these conditions affect glacial cycle scale ice sheet evolution has been little studied. The influence of subglacial hydrology and glacial sediment production and transport is therefore largely unknown. Here I present a glaciological model Glacial Systems Model (GSM) with the to-date most complete representations of fully coupled subglacial hydrology and sediment production and transport for the glacial cycle continental scale context. I compare the influence of of several types of subglacial hydrology drainage systems on millennial scale variability and examine the role dynamical sediment processes potentially played in the mid-Pleistocene Transition (MPT) from 41 to 100 kyr glacial cycles. Subglacial hydrology has long been inferred to play a role in glacial dynamics at decadal and shorter scales. However, it remains unclear whether subglacial hydrology has a critical role in ice sheet evolution on greater than centennial time-scales. It is also unclear which drainage system is most appropriate for the continental/glacial cycle scale. Here I compare the dynamical role of three subglacial hydrology systems most dominant in the literature in the context of surge behaviour for an idealized Hudson Strait scale ice stream. I find that subglacial hydrology is an important system inductance for realistic ice stream surging and that the three formulations all exhibit similar surge behaviour. Even a detail as fundamental as mass conserving transport of subglacial water is not necessary for simulating a full range of surge frequency and amplitude. However, one difference is apparent: the combined positive and negative feedbacks of the linked-cavity system yields longer duration surges and a broader range of effective pressures than its poro-elastic and leaky-bucket counterparts. The MPT from 41 kyr to 100 kyr glacial cycles was one of the largest changes in the Earth system over the past million years. A change from a low to high friction base under the North American Ice Complex through the removal of pre-glacial regolith has been hypothesized to play a critical role in the transition to longer and stronger glaciations. However, this hypothesis requires constraint on pre-glacial regolith cover as well as mechanistic constraints on whether the appropriate amount of regolith can be removed from the required regions to enable MPT occurrence at the right time. This is the first study to test the regolith hypothesis for a realistic 3D North American ice sheet that treats regolith removal as a system internal process instead of a forced soft to hard transition. The fully coupled climate, ice, subglacial hydrology, and sediment physics capture the progression of Pleistocene glacial cycles within parametric and observational uncertainty. Incorporating the constraint from estimates for the present day sediment distribution, Quaternary erosion, and Atlantic Quaternary sediment volume suggests the mean Pliocene regolith thickness was 40 m or less. Given this constraint, I compare the simulated soft to hard bed transitions with the timing inferred for the MPT. The combined constraint, bedrock erosion, and sediment transport poses a challenge to the Regolith Hypothesis: denudation occurs well in advance of the MPT and the hard bedded area stays largely constant by 1.5 Ma. Furthermore, I examine the sensitivity of glacial cycle evolution to the initial thickness of the regolith in the absence of erosion. Surprisingly, thicker regolith does not delay the transition but produces large glacial cycles in the early Pleistocene even extending the length of some. This is due to the effect from higher topography on ice sheet mass balance. Therefore, I suggest that the regolith removal mechanism is not singularly responsible for the MPT, but that the MPT results from changes in many aspects of the systems. One of these aspects which remains under-studied in the literature is the long term evolution of glacierized beds over the Pleistocene

Counting Your Chickens Before They Hatch - How to Manage Rapid Venture Growth Ensuing from “Blockbuster” Crowdfunding Campaigns

Research Problem:​ While research on rapid venture growth has mostly focused on high-growth firms in later stages of development, the topic has become increasingly important to understand for new ventures as well. With the establishment of crowdfunding as an alternative source of financing, companies have access to tools that enable quick expansion of their marketing, funding and distribution capabilities that can speedily result in phases of rapid venture growth. As examples of companies that ceased to exist after a Blockbuster Kickstarter campaigns show, this phenomenon can be a double-edged sword for new ventures that fail to manage the risks and challenges associated with rapid venture growth. Research Aims​: Our aim in this thesis is to gain an in-depth understanding of the challenges arising in the aftermath of an overly successful Kickstarter campaign and analyse the strategies companies applied to overcome these challenges. Ultimately, we aim to provide insights into how new ventures manage rapid venture growth as a consequence of crowdfunding or due to other circumstances. Method​: We deploy a qualitative, comparative study approach, juxtaposing the applied strategies and concepts of six companies that continued to experience rapid growth after conducting a Blockbuster campaign on Kickstarter. Results:​ Based on the insights gained we provide an introduction into the general mindset of ventures that are managing rapid venture growth. We identify overarching concepts that guide these entrepreneurs in the areas of strategic management, company structure and growth management. Implications:​ Our results provide theoretical implications for how rapid growth can be studied in new ventures, the concept of the liability of rapid growth and the interrelatedness of the outcome of growth and the growth process research strands. Practical implications include guiding principles for new ventures inside and outside the crowdfunding context.Research Problem:​ While research on rapid venture growth has mostly focused on high-growth firms in later stages of development, the topic has become increasingly important to understand for new ventures as well. With the establishment of crowdfunding as an alternative source of financing, companies have access to tools that enable quick expansion of their marketing, funding and distribution capabilities that can speedily result in phases of rapid venture growth. As examples of companies that ceased to exist after a Blockbuster Kickstarter campaigns show, this phenomenon can be a double-edged sword for new ventures that fail to manage the risks and challenges associated with rapid venture growth. Research Aims​: Our aim in this thesis is to gain an in-depth understanding of the challenges arising in the aftermath of an overly successful Kickstarter campaign and analyse the strategies companies applied to overcome these challenges. Ultimately, we aim to provide insights into how new ventures manage rapid venture growth as a consequence of crowdfunding or due to other circumstances. Method​: We deploy a qualitative, comparative study approach, juxtaposing the applied strategies and concepts of six companies that continued to experience rapid growth after conducting a Blockbuster campaign on Kickstarter. Results:​ Based on the insights gained we provide an introduction into the general mindset of ventures that are managing rapid venture growth. We identify overarching concepts that guide these entrepreneurs in the areas of strategic management, company structure and growth management. Implications:​ Our results provide theoretical implications for how rapid growth can be studied in new ventures, the concept of the liability of rapid growth and the interrelatedness of the outcome of growth and the growth process research strands. Practical implications include guiding principles for new ventures inside and outside the crowdfunding context